The medicare wages and tips box of your W-2 is supposed to be the same your wages, tips, other compensation box. All this means is that your medicare tax is based on 100% of your earnings. Now, if there is a difference, it could be that you have a 401K, or 403K. If you add the amount from your 401 or 403 to box 1, it would probably equal box 5. If it doesn't, I would contact your employer's payroll department.
